(In answer to your Q, victorfrank, yes, an experienced jewellery maker can tell from a decent pic (clarity of the glass etc), but you don't need to be 'in the know': the real 'tell' for everyone is the price; a 12mm high standard Murano coloured glass heart (suitable for one earring) costs around £2.50+ to a jewellery maker, planing upward if foiled with silver, or yellow/white gold. Cost-in the other materials, and design/time/labour at an illegal-in-this-country £2 per hour, and the seller is still making a titanic loss if it is genuine Murano from Venice. I think this scenario is unlikely.)
Have to agree there on the clarity of the glass, I bought an electric blue wine decanter & six glasses, all decorated in 22ct gold gondolas (how twee lol) from Murano Island in the Venetian Lagoon, way back......about 30 years.
It's still as pristine as the day I bought it
Would love to know what it's worth today.....think I paid around £20, back in the seventies Murano Glass ain't cheap!
Yv x